Magneto ignition system



Jan. 11, 1966 D. c. LOUDON MAGNETO IGNITION SYSTEM Filed Dec. 5, 1960 United States Patent 3,229,162 MAGNETQ IGNITIGN SYSTEM Donald C. London, Sidney, N;Y., assignor to The Bendix Corporation, Sidney, N.Y., a corporation-of Delaware Filed Dec. 5, -1960,-Ser. No. 73,601 14 Claims. (Cl. 3'15276) rent.

A further objectof the invention lies in the provision .of apparatus of the type indicated which incorporates a vcoil having inductively coupled primary and secondary windings, the apparatus employing one or more transistors tobreak the circuit through the primary winding. Astill further object of the invention, in specific embodiments thereof, lies in the'provision of apparatus of the type indicatedincluding a .magneto having .a .coil with primary and secondarywindings, the apparatus including one or more transistors for breaking the primary .circuit :in lieu of the customary mechanical breaker points.

Yet another ob ect of the invention lies in the provision of animprovedignition circuit including a magneto,

.the parts of the circuit being particularly characterized -by their long life, -their.ab ility to sustain elevated operating temperatures for extended .periods, and by their freedomfrorn mechanical failure.

The above and further objects and novel features of the invention will more .fully appear from the following description when .the same is read in connection with the accompanying drawing. It 'is to be expressly understood, however, that the drawing is .for the purpose of illustration .only, .and is not intended as a definition of the limits of the invention.

The sole figure of the drawing isa schematic wiring diagram-of an ignition system foran internal combustion engine, such ignition system incorporating the improved apparatus for generating surges ofe lectric current in accordance with the present invention.

In the drawing, the reference character .10 designates the magneto .for an internal combustion engine, Such magnetohas a coil with a primary winding 11 and a secondary winding 12, the two windings being inductively coupled to each other and to amagnetic core .14. A rotor 13, schematically shown in the drawing, is mounted for cooperation with core '14. 'Rotor 13 carries a suitablenumber of magnetic poles, alternate ones of such mag- .netic poles being of opposite magnetic polarity. In the embodiment shown, the ignition system is designed for use with a six-cylinder fourcycle engine. Consequently, the rotor, which is driven at half engine crank shaft speed, carries six magnetic poles.

Secondary winding 12 is connected in a conventional manner to spark plugs of an engine through a distributor. One end of coil 12 is connected to ground by a wire 15. The other end of coil 12 is connected to the center post of the rotor 16 of a distributor 17 by a wire 18. Rotor 16 sequentially cooperates with six angularly spaced contacts, each of which is connected by a wire 19 to one terminal of its spark plug 20. The other terminals of the spark plugs are connected to ground as through the block of the motor (not shown) and a wire 21.

The ends of the primary winding 11 are periodically connected together in a manner approaching a short cirtransistor is connected to wire 24 by a wire 41.

3,229,162 Patented Jan. 11, 1966 ice cuit, such circuit thereafter being broken in order to induce a substantial voltage insecondary winding 12. Such induced voltage causes acurrent surge in discharge circuit 15, '18 and thus the firing of'the' particular spark plug whose contact them cooperates with-distributor rotor 16. The primary circuit of the inventioninclude s transistor. means for effecting the closing and breaking of the circuit, thereby eliminating the mechanically operated breaker points customarily employed'for such purpose.

One end-of primary winding 11 is connectedto a first end of winding '25 of a coil 26 by a wire 22,as shown. The otherend ofwinding 11 is connected by a wire 24 to the corresponding, first end of a second winding 27 of coil 26. Coil 26 has a saturable magnetic core '29 which may be made of the magnetic core material known is connected -by a Wire 30 to the base 31'o-f a first'transistor 32. The emitter 34 of transistor 32 is connected to wire 22 by a wire-35. A second transistor 39-is connected in the same 'rnanrie'rbetween the second end of Winding 27 of coil 26 and wire 24. Thus a wire 36 extendsfrom the second end of winding 27 to the base 37 of a second transistor 39, and the emitter 40 of "the second The collector 42 of transistor 32 and the collector 44 of transistor 39 are connected by a wire 45 which in turn is connected to ground by wire 4o. A resistor 47 is connected across wires 31) and '36, as shown, to initate conduction of the transistor. The magneto and the circuit associated therewith, which has been described above, functions as follows: Assume that the rotor 13 is in such position relative to core 14 that the flux through'the core 14 has reached a positive maximum and has started to decrease. Assume also that the parts are so disposed that such action causes the wire 22 to be slightly positive. This makes emitter 34 of transistor '32 positive with respect to the'base31 of such transistor by reason of the connection between them made up of wire 30, resistor 47, wire 36, winding 27, wire 24, winding 11, andwires 22 and 35. As a result, a current flows from emitter 3 1 to base 31, thereby turning transistor 32 on, that is, lowering the resistance between its emitter-and the collector. Therefore, increased current now flows from "the emitter to the collector 42 of transistor 32, through the collector 44 to base 37 of transistor 39 through coil 27 and through winding 11. By transformer feedback action in coil 26 the rising current flow through winding 27 of such coil causes a' current flow in winding 25, thus further increasing the base drive of transistor 32, still further causing .the circuit across primary winding 11 of the magneto to approach short circuited condition. The circuit remains in this virtually short circuitedstate as long as the current fiow through it is increasing. When such current reaches its peak value, the base drive voltage of winding 25 of coil 26 reverses its polarity, thereby causing transistor 32 to turn off. This interrupts the current flowing through primary winding '11, thereby inducing a voltage in secondary winding 12. It will be seen that during this ,portion of the operating cycle, transistor 39 remains nonconductive between emitted 40 and collector 44.

The operation of the circuit in the other half-cycle is the same, except that transistor 39 is then operative and transistor 32 is inoperative so far as high gain transistor ,action is concerned. Such half-cycle starts when the rotor flux through the core 14 has passed through the negative maximum and has started to increase in absolute value, causing the wire 24 to be slightly positive. This makes the emitter 40 of transistor 39 positive with respect to its base 37 through win-ding 25 and resistor 47. This emitter to base current causes transistor 39 to turn on, that is, its emitter to collector resistance is lowered. Therefore, increased current flows through the emitter to the collector of transistor 39 and through winding 25 via transistor 32. The transformer feedback action between windings 25 and 27 causes the base drive of transistor 39 to increase, still further causing the circuit across primary winding 11 to approach a short circuited state. Such circuit stays in this state as long as the current through primary winding 11 is increasing. When the current reaches its peak value, the base drive voltage of winding 27 reverses its polarity, thereby causing transistor 39 to turn off. This interrupts the primary current through winding 11, resulting in high secondary voltage output from winding 12, as before.

It will be seen from the above that should it be desired to utilize only one-half of the flux reversals through core 14, one of the transistors 32 and 39 may be omitted. Thus if a circuit were desired which would yield secondary discharges on only the half-cycles first described above, transistor 39 would then be omitted along with the wires leading to its base, collector, and emitter, wire 36 being connected to ground.

Although only one embodiment of the invention has been illustrated in the accompanying drawing and described in the foregoing specification, it is to be especially understood that various changes, such as in the relative dimensions of the parts, materials used, and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art. Variations can be made in the saturation characteristics of the transformer 26 which will govern the electrical performance of the complete circuit. Thus although the cutting oif of current flow in the primary of the magneto coil has been described as taking place at the peak of the current through primary winding 11 of the magneto coil, the transformer 26 can be designed so that such current through primary 11 of the magneto coil is cut oh. when such primary current is at a desired predetermined value below such peak value. In such modification of the circuit described immediately above, the core 29 of transformer 26 is made so that its becomes saturated at the desired predetermined value below the peak value of the current through primary coil '11.

What is claimed is:

1. An ignition system including apparatus for generating surges of electric current, said apparatus comprising a magneto having a coil with inductively coupled primary and secondary windings, a magnetic core inductively associated with the windings, magnetic means cooperating with said core for subjecting the core to variations in magnetic flux, a circuit connecting the ends of the primary winding, and a transistor in the circuit for substantially closing the circuit when current in the primary winding begins to flow in one direction and for breaking the circuit when such current flow ceases to increase, whereby to produce a current surge in the secondary winding. v

2. An ignition system including apparatus for generating periodic surges of electric current, said apparatus comprising a magneto having a coil with inductively coupled primary and secondary windings, a magnetic core inductively associated with the windings, magnetic means cooperating with said core for subjecting the core to periodic variations in magnetic flux, a circuit connecting the ends of the primary winding, and a transistor connected-in series in the circuit for substantially closing the circuit when cur-rent in the primary winding begins to flow in one direction and for breaking the circuit when such current flow ceases to increase, whereby to produce a current surge in the secondary winding.

3. An ignition system as claimed in claim 2, wherein the transistor has a base, an emitter, and a collector, and the emitter and collector are connected in series in the said circuit.

4. An ignition system as claimed in claim 2, comprising a second coil having inductively coupled first and second windings, the first winding of the second coil being connected in series in said circuit, and the second winding of the second coil being connected in shunt with the transistor, whereby to increase the current flow through the transistor when current in the primary winding begins to flow in said one direction.

5. An ignition system as claimed in claim 4, wherein the transistor has a base, an emitter, and a collector, and the emitter and collector are connected in series in said circuit.

6. An ignition system as claimed in claim 5, compris ing a current-starting resistor in said circuit connected in series with the first winding of the second coil.

7. An ignition system including apparatus for generating periodic surges of electric current, said apparatus comprising a magneto having a coil with inductively coupled primary and secondary windings, a magnetic core inductively associated with the windings, magnetic means cooperating with said core for subjecting the core to periodically reversing magnetic flux, a circuit connecting the ends of the primary winding, a first transistor connected in series in the circuit for substantially closing the circuit when current in the primary winding begins to flow therein in a first direction and for breaking the circuit when such current flow in the first direction ceases to increase, and a second transistor connected in series in the circuit for substantially closing the circuit when current in the primary wnding begins to flow therein in the second, reverse, direction and for breaking the circuit when such current flow in the second direction ceases to increase, whereby to produce periodic current surges in the secondary winding.

8. Ignition apparatus which comprises a magneto having a coil with inductively coupled primary and secondary windings, a magnetic core inductively associated with the windings, a rotor having magnetic poles for subjecting the core to periodically reversing magnetic flux, a discharge circuit connected to the secondary winding, a primary circuit connecting the ends of the primary winding, a first transistor connected in series in the primary circuit for substantially closing the primary circuit when current in the primary winding begins to flow therein in a first direction and for breaking the primary circuit when such current flow in the first direction ceases to increase, and a second transistor connected in series in the primary circuit for substantially closing the primary circuit when current in the primary winding begins to flow therein in the second, reverse, direction and for breaking the primary circuit when such current flow in the second direction ceases to increase, whereby to produce periodic current surges in the secondary winding.

9. An ignition system as claimed in claim 8, wherein each of the transistors has a base, an emitter, and a collector, the emitter and collector of each transistor are connected in series in said circuit, and the collectors of the transistors are connected.

10. An ignition system apparatus as claimed in claim 9, comprising asecond coil having inductively coupled first and second windings, the first winding of the second coil being connected in series with the base of the first transistor, the second winding of the second coil being connected in series with the base of the second transistor, and a current-starting resistor connecting the bases of the transistors.

11. An ignition system including apparatus for generating surges of electric current, said apparatus comprising a magneto having a coil with inductively coupled primary and secondary windings, a magnetic core inductively associated with the windings, magnetic means cooperating with said core for subjecting the core to variations in magnetic flux, a circuit connecting the ends of the primary winding, and a transistor in the circuit for substantially closing the circuit when current in the primary winding begins to flow in one direction and for breaking the circuit when such current flow reaches a predetermined desired value, whereby to produce a current surge in the secondary winding.

12. An ignition system including apparatus for generating periodic surges of electric current, said apparatus comprising a magneto having a coil with inductively coupled primary and secondary windings, a magnetic core inductively associated with the windings, magnetic means cooperating with said core for subjecting the core to periodically reversing magnetic flux, a circuit connecting the ends of the primary winding, a first transistor connected in series in the circuit for substantially closing the circuit when current in the primary winding begins to flow therein in a first direction and for breaking the circuit when such current flow in the first direction reaches a predetermined desired value, and a second transistor connected in series in the circuit for substantially closing the circuit when current in the primary Winding begins to fiow therein in the second, reverse, direction and for breaking the circuit when such current fiow in the second direction reaches a predetermined desired value, whereby to produce periodic current surges in the secondary winding.

13. Ignition apparatus which comprises a magneto having a coil with inductively coupled primary and secondary windings, a magnetic core inductively associated with the windings, a rotor having magnetic poles for subjecting the core to periodically reversing magnetic flux, a discharge circuit connected to the secondary winding, a primary circuit connecting the ends of the primary winding, a firs-t transistor connected in series in the primary circuit for substantially closing the primary circuit when current in the primary winding begins to flow therein in a first direction and for breaking the primary circuit when such current flow in the first direction reaches a predetermined desired value, and a second transistor connected in series in the primary circuit for substantially closing the primary circuit when current in the primary Winding begins to flow therein in the second, reverse, direction and for breaking the primary circuit when such current flow in the second direction reaches a predetermined desired value, whereby to produce periodic current surges in the secondary Winding.

14. Apparatus of the class described comprising in combination a magneto including a transformer having primary and secondary windings on a magnetic core and a magnetic rotor operatively associated with said transformer to generate alternating current flow in said primary winding, means connected with said primary winding to control current flow therein comprising first and second transistors each having an emitter, a collector and a base, means connecting the collectors of said transistors to each other, means connecting the emitter of the first transistor to one end of said primary winding and the emitter of the second transistor to the other end of said primary winding, a resistor connected between the bases of said transistors, and a second transformer comprising first and second inductively coupled windings wound on a saturable magnetic core, said first Winding being connected between said one end of the primary winding and the base of said first transistor and said second winding being connected between said other end of said primary winding and the base of said second transistor, and an igniter gap having spaced electrodes connected to opposite ends of said secondary winding.

References Cited by the Examiner UNITED STATES PATENTS 2,3 82,808 8/1945 Ochsenbein 315-218 X 2,863,099 12/1958 Smits 315218 2,949,565 8/ 1960 Rohloff. 2,953,719 9/1960 Guiot. 2,976,461 3/1961 Dilger 315-209 GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, Examiners. 

14. APPARATUS OF THE CLASS DESCRIBED COMPRISING IN COMBINATION A MAGNETO INCLUDING A TRANSFORMER HAVING PRIMARY AND SECONDARY WINDINGS ON A MAGNETIC CORE AND A MAGNETIC ROTOR OPERATIVELY ASSOCIATED WITH SAID TRANSFORMER TO GENERATE ALTERNATING CURRENT FLOW IN SAID PRIMARY WINDING, MEANS CONNECTED WITH SAID PRIMARY WINDING TO CONTROL CURRENT FLOW THEREIN COMPRISING FIRST AND SECOND TRANSISTORS EACH HAVING AN EMITTER, A COLLECTOR AND A BASE, MEANS CONNECTING THE COLLECTORS OF SAID TRANSISTORS TO EACH OTHER, MEANS CONNECTING THE EMITTER OR THE FIRST TRANSISTOR TO ONE END OF SAID PRIMARY WINDING AND THE EMITTER OF THE SECOND TRANSISTOR TO THE OTHER END OF SAID PRIMARY WINDING, A RESISTOR CONNECTED BETWEEN THE BASES OF SAID TRANSISTORS, AND A SECOND TRANSFORMER COMPRISING FIRST AND SECOND INDUCTIVELY COUPLED WINDINGS WOUND ON A SATURABLE MAGNETIC CORE, SAID FIRST WINDING BEING CONNECTED BETWEEN SAID ONE END OF THE PRIMARY WINDING AND THE BASE OF SAID FIRST TRANSISTOR AND SAID SECOND WINDING BEING CONNECTED BETWEEN SAID OTHER END OF SAID PRIMARY WINDING AND THE BASE OF SAID SECOND TRANSISTOR, AND AN IGNITER GAP HAVING SPACED ELETRODES CONNECTED TO OPPOSITE ENDS OF SAID SECONDARY WINDING. 